NM and CM callable.
Reads a specific logical record or portion of a record from a
direct-access disk file to the data stack.
Operation Notes |
 |
This intrinsic is different than the FREAD intrinsic.
The FREAD intrinsic reads only the record already pointed to by
the logical record pointer. Issue the FREADDIR intrinsic
only for disk files composed of fixed-length or undefined-length
records. If RIO access is used, FREADDIR inputs the
specified logical record. If the record is inactive, the
contents of the inactive record are transmitted and CCE (2)
is returned; there is no indication of the block containing
some inactive records. (FCHECK returns a
nonzero error number to distinguish active and inactive records.)
If an RIO file is accessed using the non-RIO method
(NOBUF), FREADDIR inputs the specified block.
After the FREADDIR intrinsic is executed, the logical record
pointer is set to the beginning of the next logical record, or
the first logical record of the next block for NOBUF files.
It is possible to skip portions of records inadvertently, if the
multirecord aoption of FOPEN/HPFOPEN is set and
the length parameter specified is greater than one logical record.
For example, if all of record 11 and half of record 12 is read in a
file, the logical record pointer is set to the beginning of
record 13 after the FREADDIR intrinsic executes; the second
half of record 12 is skipped.
Byte stream files are applicable with FREADDIR intrinsic. The
lrecnum parameter specifies a byte offset in the byte stream
file, which is equivalent to a logical record number, since the record
size is one byte.
Not applicable to message files.
